1. Field of the Invention
The present invention relates to a linear motor, and, more particularly, to a stator of a linear motor having a plurality of outer core blocks wherein each outer core block comprises first and second side core blocks and a center core block, and the center core block has an inner diameter equal to an outer diameter of a coil block, whereby insulation and heat transfer efficiencies are improved, and the size of the linear motor is minimized.
2. Description of the Related Art
Generally, a linear compressor is an apparatus that introduces, compresses, and discharges refrigerant gas (hereinafter, referred to as “fluid”) through a linear reciprocating movement of a piston in a cylinder, which is performed by a linear driving force of a linear motor.
FIG. 1 is a longitudinal sectional view illustrating a linear compressor with a conventional linear motor mounted therein, FIG. 2 is a perspective view illustrating a stator of the conventional linear motor, FIG. 3 is a cross-sectional view of the stator of the conventional linear motor shown in FIG. 2, and FIG. 4 is a longitudinal sectional view of the stator of the conventional linear motor shown in FIG. 2.
Referring to FIG. 1, the linear compressor comprises: a shell 2; and a linear compression unit 4 disposed in the shell 2 for compressing fluid.
The linear compression unit 4 comprises: a cylinder block 8 having a cylinder 6; a back cover 12 having a fluid inlet port 10; a piston 14 disposed such that the piston 14 performs a linear reciprocating movement in the cylinder 6; a linear motor 20 for generating a driving force necessary for the piston 14 to perform the linear reciprocating movement in the cylinder 6; an outlet valve assembly 16 disposed in the front of the cylinder 6 for discharging the fluid compressed in the cylinder 6.
As shown in FIGS. 1 to 3, the linear motor 20 comprises a stator and a mover.
The stator comprises: a plurality of outer cores 21; an inner core 24 disposed while being spaced a predetermined gap from the outer cores 21; and a coil block 25 mounted at the outer cores 21.
The coil block 25 comprises: a bobbin 26 extending through the outer cores 21; and a coil 27 wound on the bobbin 26 for creating a magnetic field.
The mover comprises: a magnet 28 disposed between the outer cores 21 and the inner core 24 while being spaced a predetermined gap from the outer cores 21 and the inner core 24; and a magnet frame 29, to which the magnet 28 is securely fixed.
As shown in FIGS. 2 and 3, the outer cores 21 are disposed at the outer circumferential surface of the coil block 25 at predetermined intervals in the circumferential direction.
Each outer core 21 comprises: a first outer core block 22, which is formed of a plurality of stacked core sheets; and a second outer core block 23, which is formed of a plurality of stacked core sheets. The first and second outer core blocks 22 and 23 are opposite to each other while being in contact with each other.
For stability, each outer core 21 must be spaced a predetermined insulation distance from the coil block 25. Consequently, the inner circumferential surface of each outer core 21 is spaced apart from the outer circumferential surface of the coil block 25 by the above-mentioned insulation distance.
When the linear motor 20 is designed, the inner diameter R21 of each outer core 21 is set such that the outer core 21 is spaced a predetermined gap from the magnet 28.
As shown in FIG. 3, the inner diameter R21 of each outer core 21 does not exactly correspond to the outer diameter R25 of the coil block 25, and therefore, the distance between an inner circumferential surface 30 of the outer core 21 and an outer circumferential surface 31 of the coil block 25 is not uniform.
Specifically, the distance tc between the inner circumferential surface 30 of each outer core 21 and the outer circumferential surface 31 of the coil block 25 at the center of the outer core 21 is greater than the distance tc between the inner circumferential surface 30 of each outer core 21 and the outer circumferential surface 31 of the coil block 25 at opposite sides of the outer core 21.
As described above, each outer core 21 must be spaced from the core block 25 by the predetermined insulation distance. Consequently, the distance tc between the inner circumferential surface 30 of each outer core 21 and the outer circumferential surface 31 of the coil block 25 at the opposite sides of the outer core 21 is set to the predetermined insulation distance.
In the stator of the conventional linear motor, however, unnecessary space is excessively formed between the inner circumferential surface 30 of each outer core 21 and the outer circumferential surface 31 of the coil block 25 at the center of the outer core 21, if the distance tc between the inner circumferential surface 30 of each outer core 21 and the outer circumferential surface 31 of the coil block 25 at the opposite sides of the outer core 21 is set to the predetermined insulation distance. As a result, the size of the linear motor 20 is increased.
Furthermore, heat generated from the core block 25 is not smoothly transmitted to each outer core 21 due to the unnecessary space formed between the inner circumferential surface 30 of each outer core 21 and the outer circumferential surface 31 of the coil block 25 at the center of the outer core 21. As a result, heat transfer efficiency is deteriorated.
Meanwhile, if an insulating member (not shown) is disposed between the outer cores 21 and the coil block 25, friction occurs between the inner circumferential surface 30 of the outer core 21 and the insulating member, since the distance between the inner circumferential surface 30 of the outer core 21 and the outer circumferential surface 31 of the coil block 25 is not uniform. As a result, the insulating member is damaged.